System Call Queue Between Visible and Invisible Computing Devices

ABSTRACT

Embodiments described herein include a system, a computer-readable medium and a computer-implemented method for processing a system call (SYSCALL) request. The SYSCALL request from an invisible processing device is stored in a queueing mechanism that is accessible to a visible processing device, where the visible processing device is visible to an operating system and the invisible processing device is invisible to the operating system. The SYSCALL request is processed using the visible processing device, and the invisible processing device is notified using a notification mechanism that the SYSCALL request was processed.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 61/617,483, filed on Mar. 29, 2012 and is incorporated by reference in its entirety.

BACKGROUND

1. Field of the Invention

The present invention is generally directed to computing systems. More particularly, the present invention is directed to processing system calls within a computing system.

2. Background Art

The desire to use a graphics processing unit (GPU) for general computation has become much more pronounced recently due to the GPU's exemplary performance per unit power and/or cost. The computational capabilities for GPUs, generally, have grown at a rate exceeding that of the corresponding central processing unit (CPU) platforms. This growth, coupled with the explosion of the mobile computing market and its necessary supporting server/enterprise systems, has been used to provide a specified quality of desired user experience. Consequently, the combined use of CPUs and GPUs for executing workloads with data parallel content is becoming a volume technology.

However, GPUs have traditionally operated in a constrained programming environment, available only for the acceleration of graphics. These constraints arose from the fact that GPUs did not have as rich a programming ecosystem as CPUs. Their use, therefore, has been mostly limited to two dimensional (2-D) and three dimensional (3-D) graphics and a few leading edge multimedia applications, which are already accustomed to dealing with graphics and video application programming interfaces (APIs).

With the advent of multi-vendor supported OpenCL® and DirectCompute®, standard APIs and supporting tools, the limitations of the GPUs in traditional applications has been extended beyond traditional graphics. Although OpenCL and DirectCompute are a promising start, there are many hurdles remaining to creating an environment and ecosystem that allows the combination of the CPU and GPU to be used as fluidly as the CPU for most programming tasks.

Existing computing systems often include multiple processing devices. For example, some computing systems include both a CPU and a GPU on separate chips (e.g., the CPU might be located on a motherboard and the GPU might be located on a graphics card) or in a single chip package. Both of these arrangements, however, still include significant challenges associated with (i) separate memory systems, (ii) efficient scheduling, (iii) providing quality of service (QoS) guarantees between processes, (iv) programming model, and (v) compiling to multiple target instruction set architectures (ISAs)—all while minimizing power consumption.

For example, the discrete chip arrangement forces system and software architects to utilize chip to chip interfaces for each processor to access memory. While these external interfaces (e.g., chip to chip) negatively affect memory latency and power consumption for cooperating heterogeneous processors, the separate memory systems (i.e., separate address spaces) and driver managed shared memory create overhead that becomes unacceptable for fine grain offload.

In another example, in computing systems that include a CPU and a GPU, certain commands cannot be executed using a GPU. For example, in a conventional system a GPU cannot make system calls because the GPU is not visible to the operating system (OS). A system call (SYSCALL) is a mechanism used by an application for requesting services from the kernel of the OS. Example services may include memory allocation, thread management, printing, or other services that may be required from the OS. When a processor (such as, for example, a GPU or other device) cannot process tasks because it is not visible (hereinafter an invisible processor), and therefore, does not have access to an OS, inefficiencies are created as the invisible processor cannot process a task, and may be idle, When remaining processes in the system are utilized or over utilized.

SUMMARY OF EMBODIMENTS

What is needed, therefore, are systems and methods for allowing an invisible processor to make system calls to the OS through a request to a visible processor (e.g., another device or processor such as, for example, a CPU) (hereinafter a “visible processor”).

Embodiments of the present invention include scheduling techniques to efficiently and simultaneously launch two or more tasks between a visible and invisible processor (e.g., within an accelerated processing device). The ability to simultaneously launch two or more tasks enables full utilization of the CPU's resources.

Although GPUs, accelerated processing units (APUs), and general purpose use of the graphics processing unit (GPGPU) are commonly used terms in this field, the expression “accelerated processing device (APD)” is considered to be a broader expression. For example, APD refers to any cooperating collection of hardware and/or software that performs those functions and computations associated with accelerating graphics processing tasks, data parallel tasks, or nested data parallel tasks in an accelerated manner compared to conventional CPUs, conventional GPUs, software and/or combinations thereof.

Embodiments described herein include a system, a computer-readable medium and a computer-implemented method for processing a system call (SYSCALL) request. The SYSCALL request from an invisible processing device is stored in a queueing mechanism that is accessible to a visible processing device. The visible processing device is visible to an operating system and the invisible processing device is invisible to the operating system. The SYSCALL request is processed using the visible processing device, and the invisible processing device is notified using a notification mechanism that the SYSCALL request was processed.

Further features and advantages of the invention, as well as the structure and operation of various embodiments of the invention, are described in detail below with reference to the accompanying drawings. It is noted that the invention is not limited to the specific embodiments described herein. Such embodiments are presented herein for illustrative purposes only. Additional embodiments will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein.

BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES

The accompanying drawings, which are incorporated herein and form part of the specification, illustrate the present invention and, together with the description, further serve to explain the principles of the invention and to enable a person skilled in the pertinent art to make and use the invention. Various embodiments of the present invention are described below with reference to the drawings, wherein like reference numerals are used to refer to like elements throughout.

FIG. 1A is an illustrative block diagram of a processing system in accordance with embodiments of the present invention.

FIG. 1B is an illustrative block diagram illustration of the APD illustrated in FIG. 1A.

FIG. 2 is a block diagram that includes components for making a system call to an operating system by a processing device invisible to the operating system, according to an embodiment.

FIG. 3 is a flowchart of a method for processing a system call from a processing device invisible to an operating system, according to an embodiment.

DETAILED DESCRIPTION OF THE EMBODIMENTS

In the detailed description that follows, references to “one embodiment,” “an embodiment,” “an example embodiment,” etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

The term “embodiments of the invention” does not require that all embodiments of the invention include the discussed feature, advantage or mode of operation. Alternate embodiments may be devised without departing from the scope of the invention, and well-known elements of the invention may not be described in detail or may be omitted so as not to obscure the relevant details of the invention. In addition, the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. For example, as used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises,” “comprising,” “includes” and/or “including,” when used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

FIG. 1A is an exemplary illustration of a unified computing system 100 including two processors, a CPU 102 and an APD 104. CPU 102 can include one or more single or multi core CPUs. In one embodiment of the present invention, the system 100 is formed on a single silicon die or package, combining CPU 102 and APD 104 to provide a unified programming and execution environment. This environment enables the APD 104 to be used as fluidly as the CPU 102 for some programming tasks. However, it is not an absolute requirement of this invention that the CPU 102 and APD 104 be formed on a single silicon die. In some embodiments, it is possible for them to be formed separately and mounted on the same or different substrates.

In one example, system 100 also includes a memory 106, an OS 108, and a communication infrastructure 109. The OS 108 and the communication infrastructure 109 are discussed in greater detail below.

The system 100 also includes a kernel mode driver (KMD) 110, a software scheduler (SWS) 112, and a memory management unit 116, such as input/output memory management unit (IOMMU). Components of system 100 can be implemented as hardware, firmware, software, or any combination thereof. A person of ordinary skill in the art will appreciate that system 100 may include one or more software, hardware, and firmware components in addition to, or different from, that shown in the embodiment shown in FIG. 1A.

In one example, a driver, such as KMD 110, typically communicates with a device through a computer bus or communications subsystem to which the hardware connects. When a calling program invokes a routine in the driver, the driver issues commands to the device. Once the device sends data back to the driver, the driver may invoke routines in the original calling program. In one example, drivers are hardware-dependent and operating-system-specific. They usually provide the interrupt handling required for any necessary asynchronous time-dependent hardware interface.

Device drivers, particularly on modem Microsoft Windows® platforms, can run in kernel-mode (Ring 0) or in user-mode (Ring 3). The primary benefit of running a driver in user mode is improved stability, since a poorly written user mode device driver cannot crash the system by overwriting kernel memory. On the other hand, user/kernel-mode transitions usually impose a considerable performance overhead, thereby prohibiting user mode-drivers for low latency and high throughput requirements. Kernel space can be accessed by user module only through the use of system calls. End user programs like the UNIX shell or other GUI based applications are part of the user space. These applications interact with hardware through kernel supported functions.

CPU 102 can include (not shown) one or more of a control processor, field programmable gate array (FPGA), application specific integrated circuit (ASIC), or digital signal processor (DSP). CPU 102, for example, executes the control logic, including the OS 108, KMD 110, SWS 112, and applications 111, that control the operation of computing system 100. In this illustrative embodiment, CPU 102, according to one embodiment, initiates and controls the execution of applications 111 by, for example, distributing the processing associated with that application across the CPU 102 and other processing resources, such as the APD 104.

APD 104, among other things, executes commands and programs for selected functions, such as graphics operations and other operations that may be, for example, particularly suited for parallel processing. In general, APD 104 can be frequently used for executing graphics pipeline operations, such as pixel operations, geometric computations, and rendering an image to a display. In various embodiments of the present invention, APD 104 can also execute compute processing operations (e.g., those operations unrelated to graphics such as, for example, video operations, physics simulations, computational fluid dynamics, etc.), based on commands or instructions received from CPU 102.

For example, commands can be considered as special instructions that are not typically defined in the instruction set architecture (ISA). A command may be executed by a special processor such a dispatch processor, command processor, or network controller. On the other hand, instructions can be considered, for example, a single operation of a processor within a computer architecture. In one example, when using two sets of ISAs, some instructions are used to execute x86 programs and some instructions are used to execute kernels on an APD unit.

In an illustrative embodiment, CPU 102 transmits selected commands to APD 104. These selected commands can include graphics commands and other commands amenable to parallel execution. These selected commands, that can also include compute processing commands, can be executed substantially independently from CPU 102.

APD 104 can include its own compute units (not shown), such as, but not limited to, one or more SIMD processing cores. As referred to herein, a SIMD is a pipeline, or programming model, where a kernel is executed concurrently on multiple processing elements each with its own data and a shared program counter. All processing elements execute an identical set of instructions. The use of predication enables work-items to participate or not for each issued command.

In one example, each APD 104 compute unit can include one or more scalar and/or vector floating-point units and/or arithmetic and logic units (ALUs). The APD compute unit can also include special purpose processing units (not shown), such as inverse-square root units and sine/cosine units. In one example, the APD compute units are referred to herein collectively as shader core 122.

Having one or more SIMDs, in general, makes APD 104 ideally suited for execution of data-parallel tasks such as those that are common in graphics processing.

Some graphics pipeline operations, such as pixel processing, and other parallel computation operations, can require that the same command stream or compute kernel be performed on streams or collections of input data elements. Respective instantiations of the same compute kernel can be executed concurrently on multiple compute units in shader core 122 in order to process such data elements in parallel. As referred to herein, for example, a compute kernel is a function containing instructions declared in a program and executed on an APD. This function is also referred to as a kernel, a shader, a shader program, or a program.

In one illustrative embodiment, each APD compute unit (e.g., SIMD processing core) can execute a respective instantiation of a particular work-item to process incoming data. A work-item is one of a collection is of parallel executions of a kernel invoked on a device by a command. A work-item can be executed by one or more processing elements as part of a work-group executing on an APD compute unit.

A work-item is distinguished from other executions within the collection by its global ID and local ID. In one example, a subset of work-items in a workgroup that execute simultaneously together on a SIMD can be referred to as a wavefront 136. The width of a wavefront is a characteristic of the hardware of the compute unit (e.g., SIMD processing core). As referred to herein, a workgroup is a collection of related work-items that execute on a single compute unit. The work-items in the group execute the same kernel and share local memory and work-group barriers.

In the exemplary embodiment, all wavefronts from a workgroup are processed on the same SIMD processing core. Instructions across a wavefront are issued one at a time, and when all work-items follow the same control flow, each work-item executes the same program. Wavefronts can also be referred to as warps, vectors, or threads.

An execution mask and work-item predication are used to enable divergent control flow within a wavefront, where each individual Work-item can actually take a unique code path through the kernel. Partially populated wavefronts can be processed when a full set of work-items is not available at wavefront start time. For example, shader core 122 can simultaneously execute a predetermined number of wavefronts 136, each wavefront 136 comprising a multiple work-items.

Within the system 100, APD 104 includes its own memory, such as graphics memory 130 (although memory 130 is not limited to graphics only use). Graphics memory 130 provides a local memory for use during computations in APD 104. Individual compute units (not shown) within shader core 122 can have their own local data store (not shown). In one embodiment, APD 104 includes access to local graphics memory 130, as well as access to the memory 106. In another embodiment, APD 104 can include access to dynamic random access memory (DRAM) or other such memories (not shown) attached directly to the APD 104 and separately from memory 106.

In the example shown, APD 104 also includes one or “n” number of command processors (CPs) 124. CP 124 controls the processing within APD 104, CP 124 also retrieves commands to be executed from command buffers 125 in memory 106 and coordinates the execution of those commands on APD 104.

In one example, CPU 102 inputs commands based on applications 111 into appropriate command buffers 125. As referred to herein, an application is the combination of the program parts that will execute on the compute units within the CPU and APD.

A plurality of command buffers 125 can be maintained with each process scheduled for execution on the APD 104.

CP 124 can be implemented in hardware, firmware, or software, or a combination thereof In one embodiment, CP 124 is implemented as a reduced instruction set computer (RISC) engine with microcode for implementing logic including scheduling logic.

APD 104 also includes one or “n” number of dispatch controllers (DCs) 126 in the present application, the term dispatch refers to a command executed by a dispatch controller that uses the context state to initiate the start of the execution of a kernel for a set of work groups on a set of compute units. DC 126 includes logic to initiate workgroups in the shader core 122. In some embodiments, DC 126 can be implemented as part of CP 124.

System 100 also includes a hardware scheduler (HWS) 128 for selecting a process from a run list 150 for execution on APD 104. HWS 128 can select processes from run list 150 using round robin methodology, priority level, or based on other scheduling policies. The priority level, for example, can be dynamically determined. HWS 128 can also include functionality to manage the run list 150, for example, by adding new processes and by deleting existing processes from run-list 150. The run list management logic of HWS 128 is sometimes referred to as a run list controller (RLC).

In various embodiments of the present invention, when HWS 128 initiates the execution of a process from run list 150, CP 124 begins retrieving and executing commands from the corresponding command buffer 125. In some instances, CP 124 can generate one or more commands to be executed within APD 104, which correspond with commands received from CPU 102. In one embodiment, CP 124, together with other components, implements a prioritizing and scheduling of commands on APD 104 in a manner that improves or maximizes the utilization of the resources of APD 104 resources and/or system 100.

APD 104 can have access to, or may include, an interrupt generator 146. Interrupt generator 146 can be configured by APD 104 to interrupt the OS 108 when interrupt events, such as page faults, are encountered by APD 104. For example, APD 104 can rely on interrupt generation logic within IOMMU 116 to create the page fault interrupts noted above.

APD 104 can also include preemption and context switch logic 120 for preempting a process currently running within shader core 122. Context switch logic 120, for example, includes functionality to stop the process and save its current state (e.g., shader core 122 state, and CP 124 state).

As referred to herein, the term state can include an initial state, an intermediate state, and/or a final state. An initial state is a starting point for a machine to process an input data set according to a programming order to create an output set of data. There is an intermediate state, for example, that needs to be stored at several points to enable the processing to make forward progress. This intermediate state is sometimes stored to allow a continuation of execution at a later time when interrupted by some other process. There is also final state that can be recorded as part of the output data set.

Preemption and context switch logic 120 can also include logic to context switch another process into the APD 104. The functionality to context switch another process into running on the APD 104 may include instantiating the process, for example, through the CP 124 and DC 126 to run on APD 104, restoring any previously saved state for that process, and starting its execution.

Memory 106 can include non-persistent memory such as DRAM (not shown). Memory 106 can store, e.g., processing logic instructions, constant values, and variable values during execution of portions of applications or other processing logic. For example, in one embodiment, parts of control logic to perform one or more operations on CPU 102 can reside within memory 106 during execution of the respective portions of the operation by CPU 102.

During execution, respective applications, OS functions, processing logic commands, and system software can reside in memory 106. Control logic commands fundamental to OS 108 will generally reside in memory 106 during execution. Other software commands, including, for example, kernel mode driver 110 and software scheduler 112 can also reside in memory 106 during execution of system 100.

In this example, memory 106 includes command buffers 125 that are used by CPU 102 to send commands to APD 104. Memory 106 also contains process lists and process information (e.g., active list 152 and process control blocks 154). These lists, as well as the information, are used by scheduling software executing on CPU 102 to communicate scheduling information to APD 104 and/or related scheduling hardware. Access to memory 106 can be managed by a memory controller 140, which is coupled to memory 106. For example, requests from CPU 102, or from other devices, for reading from or for writing to memory 106 are managed by the memory controller 140.

Referring back to other aspects of system 100, IOMMU 116 is a multi-context memory management unit.

As used herein, context can be considered the environment within which the kernels execute and the domain in which synchronization and memory management is defined. The context includes a set of devices, the memory accessible to those devices, the corresponding memory properties and one or more command-queues used to schedule execution of a kernel(s) or operations on memory objects.

Referring back to the example shown in FIG. 1A, IOMMU 116 includes logic to perform virtual to physical address translation for memory page access for devices including APD 104. IOMMU 116 may also include logic to generate interrupts, for example, when a page access by a device such as APD 104 results in a page fault. IOMMU 116 may also include, or have access to, a translation lookaside buffer (TLB) 118. TLB 118, as an example, can be implemented in a content addressable memory (CAM) to accelerate translation of logical (i.e., virtual) memory addresses to physical memory addresses for requests made by APD 104 for data in memory 106.

In the example shown, communication infrastructure 109 interconnects the components of system 100 as needed. Communication infrastructure 109 can include (not shown) one or more of a peripheral component interconnect (PCI) bus, extended PCI (PCI-E) bus, advanced microcontroller bus architecture (AMBA) bus, advanced graphics port (AGP), or other such communication infrastructure. Communications infrastructure 109 can also include an Ethernet, or similar network, or any suitable physical communications infrastructure that satisfies an application's data transfer rate requirements. Communication infrastructure 109 includes the functionality to interconnect components including components of computing system 100.

In this example, OS 108 includes functionality to manage the hardware components of system 100 and to provide common services. In various embodiments, OS 108 can execute on CPU 102 and provide common services. These common services can include, for example, scheduling applications for execution within CPU 102, fault management, interrupt service, as well as processing the input and output of other applications.

In some embodiments, based on interrupts generated by an interrupt controller, such as interrupt controller 148, OS 108 invokes an appropriate interrupt handling routine. For example, upon detecting a page fault interrupt, OS 108 may invoke an interrupt handler to initiate loading of the relevant page into memory 106 and to update corresponding page tables.

OS 108 may also include functionality to protect system 100 by ensuring that access to hardware components is mediated through OS managed kernel functionality. In effect, OS 108 ensures that applications, such as applications 111, run on CPU 102 in user space. OS 108 also ensures that applications 111 invoke kernel functionality provided by the OS to access hardware and/or input/output functionality.

By way of example, applications 111 include various programs or commands to perform user computations that are also executed on CPU 102. CPU 102 can seamlessly send selected commands for processing on the APD 104. In one example, KMD 110 implements an application program interface (API) through which CPU 102, or applications executing on CPU 102 or other logic, can invoke APD 104 functionality. For example, KMD 110 can enqueue commands from CPU 102 to command buffers 125 from which APD 104 will subsequently retrieve the commands. Additionally, KMD 110 can, together with SWS 112, perform scheduling of processes to be executed on APD 104. SWS 112, for example, can include logic to maintain a prioritized list of processes to be executed on the APD.

In other embodiments of the present invention, applications executing on CPU 102 can entirely bypass KMD 110 when enqueueing commands.

In some embodiments, SWS 112 maintains an active list 152 in memory 106 of processes to be executed on APD 104. SWS 112 also selects a subset of the processes in active list 152 to be managed by HWS 128 in the hardware. Information relevant for running each process on APD 104 is communicated from CPU 102 to APD 104 through process control blocks (PCB) 154.

Processing logic for applications, OS, and system software can include commands specified in a programming language such as C and/or in a hardware description language such as Verilog, RTL, or netlists, to enable ultimately configuring a manufacturing process through the generation of maskworks/photomasks to generate a hardware device embodying aspects of the invention described herein.

A person of skill in the art will understand, upon reading this description, that computing system 100 can include more or fewer components than shown in FIG. 1A. For example, computing system 100 can include one or more input interfaces, non-volatile storage, one or more output interfaces, network interfaces, and one or more displays or display interfaces.

FIG. 1B is an embodiment showing a more detailed illustration of APD 104 shown in FIG. 1A. In FIG. 1B, CP 124 can include CP pipelines 124 a, 124 b, and 124 c, CP 124 can be configured to process the command lists that are provided as inputs from command buffers 125, shown in FIG. 1A. In the exemplary operation of FIG. 1B, CP input 0 (124 a) is responsible for driving commands into a graphics pipeline 162. CP inputs 1 and 2 (124 b and 124 c) forward commands to a compute pipeline 160. Also provided is a controller mechanism 166 for controlling operation of HWS 128.

In FIG. 1B, graphics pipeline 162 can include a set of blocks, referred to herein as ordered pipeline 164. As an example, ordered pipeline 164 includes a vertex group translator (VGT) 164 a, a primitive assembler (PA) 164 b, a scan converter (SC) 164 c, and a shader-export, render-back unit (SX/RB) 176. Each block within ordered pipeline 164 may represent a different stage of graphics processing within graphics pipeline 162. Ordered pipeline 164 can be a fixed function hardware pipeline. Other implementations can be used that would also be within the spirit and scope of the present invention.

Although only a small amount of data may be provided as an input to graphics pipeline 162, this data will be amplified by the time it is provided as an output from graphics pipeline 162. Graphics pipeline 162 also includes DC 166 for counting through ranges within work-item groups received from CP pipeline 124 a. Compute work submitted through. DC 166 is semi-synchronous with graphics pipeline 162.

Compute pipeline 160 includes shader DCs 168 and 170, Each of the DCs 168 and 170 is configured to count through compute ranges within work groups received from CP pipelines 124 b and 124 c.

The DCs 166, 168, and 170, illustrated in FIG. 1B, receive the input ranges, break the ranges down into workgroups, and then forward the workgroups to shader core 122.

Since graphics pipeline 162 is generally a fixed function pipeline, it is difficult to save and restore its state, and as a result, the graphics pipeline 162 is difficult to context switch. Therefore, in most cases context switching, as discussed herein, does not pertain to context switching among graphics processes. An exception is for graphics work in shader core 122, which can be context switched.

After the processing of work within graphics pipeline 162 has been completed, the completed work is processed through a render back unit 176, which does depth and color calculations, and then writes its final results to memory 130.

Shader core 122 can be shared by graphics pipeline 162 and compute pipeline 160. Shader core 122 can be a general processor configured to run wavefronts. In one example, all work within compute pipeline 160 is processed within shader core 122. Shader core 122 runs programmable software code and includes various forms of data, such as state data.

A disruption in the QoS occurs when all work-items are unable to access APD resources. Embodiments of the present invention facilitate efficiently and simultaneously launching two or more tasks to resources within APD 104, enabling all work-items to access various APD resources. In one embodiment, an APD input scheme enables all work-items to have access to the APD's resources in parallel by managing the APD's workload. When the APD's workload approaches maximum levels, (e.g., during attainment of maximum I/O rates), this APD input scheme assists in that otherwise unused processing resources can be simultaneously utilized in many scenarios. A serial input stream, for example, can be abstracted to appear as parallel simultaneous inputs to the APD.

By way of example, each of the CPs 124 can have one or more tasks to submit as inputs to other resources within APD 104, where each task can represent multiple wavefronts. After a first task is submitted as an input, this task may be allowed to ramp up, over a period of time, to utilize all the APD resources necessary for completion of the task. By itself, this first task may or may not reach a maximum APD utilization threshold. However, as other tasks are enqueued and are waiting to be processed within the APD 104, allocation of the APD resources can be managed to ensure that all of the tasks can simultaneously use the APD 104, each achieving a percentage of the APD's maximum utilization. This simultaneous use of the APD 104 by multiple tasks, and their combined utilization percentages, ensures that a predetermined maximum APD utilization threshold is achieved.

FIG. 2 is an illustrative block diagram 200 of a computing system environment for processing a system call request, according to an embodiment. An exemplary computing environment, such as computing system 100 described in FIGS. 1A and 1B, may include multiple computing devices that are visible and invisible to OS 108.

The environment for processing SYSCALL requests includes an OS invisible processing device 202, a queueing mechanism 204, an OS visible processing device 206, and a notification mechanism 208.

OS invisible processing device 202 is a computer processor that is not visible to OS 108. Example OS invisible processing device 202 may be APD 104, CPU 102, or a digital signal processor, etc., though the invention is not limited to those embodiments.

Although OS invisible processing device 202 is not visible to OS 108, device 202 may require OS 108 to execute SYSCALL requests. One example of a SYSCALL request can be a request for memory allocation, such as a request that processes a malloc( ) request. The malloc( ) request allocates memory for a particular process or function in system memory 106, and is known to a person skilled in the relevant art. OS invisible processing device 202 cannot process a malloc( ) request because it does not have access to OS 108, and thus cannot invoke a system request that is executed by OS 108.

In an embodiment, OS invisible processing device 202 may use OS visible processing device 206 to process SYSCALL requests on its behalf. OS visible processing device 206 may be CPU 102 or another computer processor that is visible to OS 108.

To transfer SYSCALL requests from OS invisible processing device 202 to OS visible processing device 206, device 202 may use queueing mechanism 204. Example queueing mechanism 204 may be a list, a vector, a queue, or any other data structure capable of storing and prioritizing SYSCALL requests. Queueing mechanism 204 may also be designated as a high-priority queueing mechanism. A person skilled in the art will appreciate that a high-priority queueing mechanism will have precedence for submitting tasks to, for example, processing devices within a computer environment.

For example, when queueing mechanism 204 is designated as a high-priority queueing mechanism with respect to OS visible processing device 206, OS visible processing device 206 may interrupt and save its current task to process a task stored on the high-priority queueing mechanism. Once a task from the high priority queueing mechanism is processed, OS visible processing device 206 may reinstate the interrupted task. One way to designate a queueing mechanism as being a high priority, for example, queue is to associate a different priority value with each queueing mechanism, where one priority value has precedence over other priority values.

In an embodiment, queueing mechanism 204 may be visible to OS invisible processing device 202 and OS visible processing device 206.

In an embodiment, queueing mechanism 204 may operate according to a first-in, first-out (“FIFO”) principle. Namely, the workload that is first enqueued onto queueing mechanism 204 is the workload that is first dequeued from queueing mechanism 204.

In another embodiment, OS invisible processing device 202 may pause task processing when it issues a SYSCALL request. The paused processing may resume when OS invisible processing device 202 receives a notification message that a SYSCALL request was processed.

To pass SYSCALL requests to OS visible processing device 206, SYSCALL data structure 210 can be used. SYSCALL data structure 210 includes a function parameter 212, an argument list 214 and a return value 216. Function parameter 212 includes a name of a SYSCALL function or a pointer to a SYSCALL request function in a request made by OS invisible processing device 202.

An argument list 214 includes at least one argument that may be required to execute the SYSCALL request function stored in function parameter 212. A return value 216 may be a space holder for a value that is inserted by OS visible processing device 206 that indicates whether the SYSCALL request was successfully processed or has failed.

When OS invisible processing device 202 issues a SYSCALL request, the

SYSCALL request is stored in SYSCALL data structure 210. example, OS invisible processing device 202 may include the SYSCALL request function in function parameter 212 and the required arguments (if any) in argument list 214. After SYSCALL data structure 210 is complete, OS invisible processing device 202 may store SYSCALL data structure 210 in queueing mechanism 204.

In the embodiment, OS invisible processing device 202 canon process multiple tasks in parallel. Each of those tasks can issue a SYSCALL request to OS visible processing device 206. To efficiently process multiple SYSCALL requests, OS invisible processing device 202 can create a SYSCALL vector, list or any other structure capable of storing multiple SYSCALL data structures. The SYSCALL vector can include multiple SYSCALL data structures 210 that each stores a SYSCALL request that was issued in parallel by OS invisible processing device 202. The SYSCALL data structure vector can then be included in queueing mechanism 204 that is capable of storing multiple SYSCALL data structures 210.

As queueing mechanism 204 is visible to OS visible processing device 206, OS visible processing device 206 may periodically ping queueing mechanism 204 for SYSCALL data structures 210. The frequency of each ping can be preset by OS 108 or can be configured by a system administrator.

When OS visible processing device 206 pings queueing mechanism 204 and determines that SYSCALL data structure 210 is stored therein, OS visible processing device 206 dequeues SYSCALL data structure 210. Once dequeued, OS visible processing device 206 begins to process the SYSCALL request included in SYSCALL data structure 210. Where queueing mechanism 204 stores a SYSCALL vector, OS visible processing device 206 may process each SYSCALL data structure 210 included in SYSCALL vector in sequence, or if the computing environment allows, in parallel.

In another embodiment, OS visible processing device 206 may process a task when it determines that queueing mechanism 204 stores SYSCALL data structure 210. In this embodiment, OS visible processing device 206 may interrupt the task it is currently processing and store the interrupted task in memory, such as memory 106, prior to processing the SYSCALL request. Once the SYSCALL request is processed, OS visible processing device 206 retrieves the interrupt task from memory and resumes processing the interrupted task.

To process the SYSCALL request, OS visible processing device 206 retrieves function parameter 212 and argument list 214 from SYSCALL data structure 210. Once retrieved, OS visible processing device 206 uses function parameter 212 to identify a SYSCALL function associated with SYSCALL request. It then passes arguments (if any), included in argument list 214, to the identified SYSCALL function.

When the processing is complete, OS visible processing device 206 writes the result of the SYSCALL request in return value 216 of SYSCALL data structure 210. As described herein, return value 216 indicates whether the SYSCALL request was successfully completed or has failed. In another embodiment, return value 216 may indicate a type of a notification mechanism for notifying OS invisible processing device 202 the SYSCALL request was completed.

Notification mechanism 208 notifies OS invisible processing device 202 that a SYSCALL request was completed. By way of example, notification mechanism 208 can be a queueing mechanism, similar to queueing mechanism 204. The queueing mechanism passes SYSCALL data structure 210′ to OS invisible processing device 202. SYSCALL data structure 210′ includes data, such as return value 216, that indicates that the SYSCALL request was completed or a pointer that stores the memory address of a result of the SYSCALL request.

In an embodiment where SYSCALL vector was generated, notification mechanism 208 passes the SYSCALL vector to OS invisible processing device 202. Each SYSCALL data structure 210′ included in SYSCALL vector may include result value 216 of a corresponding SYSCALL request.

FIG. 3 is a flowchart of an exemplary method 300 for making a SYSCALL request using a device invisible to the OS, according to an embodiment.

In operation 302, a device invisible to the OS generates a SYSCALL request.

The SYSCALL request is stored in SYSCALL data structure 210, as described herein. In an embodiment, once SYSCALL request is made, OS invisible processing device 202 may stop processing the task that issues the SYSCALL request until it receives a notification message that the SYSCALL request was processed.

In operation 304, an invisible device stores a SYSCALL data structure on queueing mechanism 204. Queueing mechanism 204 may be periodically monitored by OS visible processing device 206. In one embodiment, queueing mechanism 204 can be a high priority memory queue that is periodically monitored by OS visible processing device 206.

In step 306, a SYSCALL data structure is dequeued by an OS visible processing device. For example, when OS visible processing device 206 identifies that SYSCALL data structure 210 is included in queueing mechanism 204, it dequeues SYSCALL data structure 210.

In operation 308, a SYSCALL request is processed. Once SYSCALL data structure 210 is dequeued in operation 306, OS visible processing device 206 begins to process the SYSCALL request included in SYSCALL data structure 210. In one embodiment, prior to processing the SYSCALL request, OS visible processing device 206 interrupts and saves the task that it was processing when the SYSCALL request arrived.

OS visible processing device 206 begins processing by retrieving function parameter 212 and argument list 214 from SYSCALL data structure 210. Based on function parameter 212, OS visible processing device 206 selects a SYSCALL, request function that is included in SYSCALL request and processes the selected SYSCALL request function. OS visible processing device 206 may also pass the arguments from argument list 214 to the selected SYSCALL request function. Once processed, OS visible processing device 206 may write a result of the processing into result value 216.

In operation 310, a notification message is issued. Once operation 308 is complete, OS visible processing device 206 transmits a notification message to OS invisible processing device 202 that the SYSCALL request was processed.

At operation 312, a notification message is received. For example, OS invisible processing device 202 receives the notification message that the SYSCALL request was processed. Upon receipt, OS invisible processing device may continue to process instructions using the results of the processed SYSCALL request.

The Summary and Abstract sections may set forth one or more but not all exemplary embodiments of the present invention as contemplated by the inventor(s), and thus, are not intended to limit the present invention and the appended claims in any way.

Facilitate

The present invention has been described above with the aid of functional building blocks illustrating the implementation of specified functions and relationships thereof. The boundaries of these functional building blocks have been arbitrarily defined herein for the convenience of the description. Alternate boundaries can be defined so long as the specified functions and relationships thereof are appropriately performed.

The foregoing description of the specific embodiments will so fully reveal the general nature of the invention that others can, by applying knowledge within the skill of the art, readily modify and/or adapt for various applications such specific embodiments, without undue experimentation, without departing from the general concept of the present invention. Therefore, such adaptations and modifications are intended to be within the meaning and range of equivalents of the disclosed embodiments, based on the teaching and guidance presented herein. It is to be understood that the phraseology or terminology herein is for the purpose of description and not of limitation, such that the terminology or phraseology of the present specification is to be interpreted by the skilled artisan in light of the teachings and guidance.

The breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents. 

What is claimed is:
 1. A method for processing a system call (SYSCALL) request, comprising: storing a SYSCALL request from an invisible processing device in a queueing mechanism accessible to a visible processing device, wherein the visible processing device is visible to an operating system (OS) and the invisible operating device is invisible to the OS; processing the SYSCALL request using the visible processing device; and notifying the invisible processing device that the SYSCALL request was processed.
 2. The method of claim 1, further comprising: storing the SYSCALL request in a SYSCALL data structure, wherein the SYSCALL data structure includes at least a function parameter and an argument list associated with the SYSCALL request.
 3. The method of claim 1, further comprising: storing the SYSCALL request in a SYSCALL data structure, wherein the SYSCALL data structure includes at least a return value of the processed SYSCALL request.
 4. The method of claim 1, wherein the notifying further comprises: sending a notification message to the invisible processing device, wherein the notification message includes a status of the processed SYSCALL request.
 5. The method of claim 1, further comprising: pausing execution of a task that generated the SYSCALL request, the task executing on the invisible processing device; receiving a notification message that the SYSCALL request was processed by the visible processing device; and in response to the receiving, reinstating the execution of the task on the invisible processing device, wherein the invisible processing device processes a result of the SYSCALL request.
 6. The method of claim 1, further comprising: storing the processed SYSCALL request in a second queueing mechanism visible to the invisible processing device.
 7. The method of claim 1, wherein the invisible device is at least one of: an accelerated processing device (APD) and a graphics processing unit (GPU).
 8. The method of claim 1, wherein the visible processing device is a central processing unit (CPU).
 9. The method of claim 1, wherein the queueing mechanism is a high priority queue.
 10. The method of claim 1, further comprising: detecting the SYSCALL request in the queueing mechanism; in response to the detecting, pausing a task processed by the visible processing device; and resuming the paused task after the SYSCALL request was processed.
 11. A system for processing a system call (SYSCALL) request, comprising: a visible processing device configured to: access a SYSCALL request from an invisible processing device in a queueing mechanism accessible to the visible processing device, wherein the visible processing device is visible to an operating system (OS) and the invisible processing device is invisible to the OS; process the SYSCALL request; and notify the invisible processing device that the SYSCALL request was processed.
 12. The system of claim 11, wherein: a SYSCALL data structure includes the SYSCALL request, and the SYSCALL request includes at least a function parameter and an argument list associated with the SYSCALL request.
 13. The system of claim 11, wherein: a SYSCALL data structure includes the processed SYSCALL request, and the processed SYSCALL request includes at least a return value associated with the processed SYSCALL request.
 14. The system of claim 11, further comprising a notification mechanism configured to send a notification message to the invisible processing device, wherein the notification message includes a status of the processed SYSCALL request.
 15. The system of claim 11, wherein the visible processing device is further configured to: store the processed SYSCALL request in a second queueing mechanism visible to the invisible processing device.
 16. The system of claim 11, wherein the visible processing device is a central processing unit (CPU).
 17. The system of claim 11, wherein the queueing mechanism is a high priority queue.
 18. The system of claim 11, wherein the visible processing device is further configured to: detect the SYSCALL request in the queueing mechanism; pause a task processed by the visible processing device when the SYSCALL request is detected; and resume the paused task after the SYSCALL request was processed.
 19. A system for processing a system call (SYSCALL) request, comprising: an invisible processing device configured to: store a SYSCALL request in a queueing mechanism that is accessible to a visible processing device, wherein the visible processing device is visible to an operating system (OS) and the invisible processing device is invisible to the OS; receive a notification from the visible processing device that the SYSCALL request was processed by the visible processing device; and process a task based on the received notification.
 20. The system of claim 19, wherein the invisible processing device is further configured to: store the SYSCALL request in a SYSCALL data structure, wherein the SYSCALL data structure includes at least a function parameter and an argument list associated with the SYSCALL request.
 21. The system of claim 19, wherein the invisible processing device is further configured to: retrieve the SYSCALL request from a SYSCALL data structure, wherein the SYSCALL data structure includes at least a return value of the SYSCALL request that was processed by the visible processing device.
 22. The system of claim 19, further comprising a notification mechanism configured to send a notification message to the invisible processing device, wherein the notification message includes a status of the SYSCALL request processed by the visible processing device.
 23. The system of claim 19, wherein the invisible processing device is at least one of: an accelerated processing device (APD) and a graphics processing unit (GPU).
 24. The system of claim 19, wherein the invisible processing device is further configured to: pause execution of a task that generated the SYSCALL request, wherein the task executes on the invisible processing device; receive a notification message that the SYSCALL request was processed by the visible processing device; and reinstate the execution of the task on the invisible processing device, wherein the invisible processing device processes a result of the SYSCALL request once the notification is received. 